Damienne Provitolo

Spatial risks and complex systems : methodological perspectives

Research on risk and industrial catastrophes question the complexity theories. Besides the concepts of complexity which lead us to reconsider concepts of risk, hazard and vulnerability, we propose to think about more practical aspects, for example the modelling of human behaviour in crisis situations. The link between concepts as critical self-organization, emergence, bifurcation, and the methods in the Distributed Artificial Intelligence (DAI) used to model them is however difficult. nIn this paper, we present ongoing analysis on the key concepts of risk science, such as hazards and catastrophes. We propose to enrich them with complex systems theories. First, we present methodological perspectives of the DAI, for example multi-agent systems, and compare them with other simulation methods used in the context of risks. Secondly, we present the MOSAIIC model (Modelling and Simulation of Industrial Accidents by Individual-Based methods) which gives possibilities to simulate the behaviour of individuals during an industrial accident. The project and the MOSAIIC model aim to explore the effects of a major industrial accident on public health. For instance, the emission and the spread of a toxic gas in an urban environment may be a serious danger for the human health. Thus we propose to study the consequences of this type of event in order to reduce the vulnerability of the populations. In the model, we emphasize both on spatial and behavioral dimensions (ie. mobility and perception of risk). nAll these questions lead us to use different methodologies of analysis. For example, concerning mobility, the daily traffic can be simulated at a meso scale: a road axis for example. In that way, we aim to simulate the global dynamics of the network from the modelling of flows on arcs of the network n(modulated according to the time of day and the day of week). Yet, we plan to use classical models (for instance equilibrium models) because they give an ”average image” of the flows of vehicles on the arcs. Based on this first structural mobility, it is then possible to consider ”a change of level” regarding both the representation and the analysis: if a risk occurs or if a specific context disrupts the structure. As a consequence, from a management of flows on the arc, we turn to an analysis of the individual behaviours in a multi-agent system.

Structural and Dynamical Complexities of Risk and Catastrophe Systems: an Approach by System Dynamics Modelling

Risk and catastrophe are complex systems. Within the scope of this paper, we focus our attention on structural and dynamic complexities of catastrophes and on the possibility of modelling and simulating its double complexity with a formal and methodological framework: the General Systems Theory and System Dynamics modelling. Then we briefly propose a model of urban catastrophe related to a flood. After we propose some ways of research allowing exceeding the limits related to the modelling.

Mathematical Modeling of Human Behaviors During Catastrophic Events: Stability and Bifurcations

In this paper, we introduce a new approach for modeling the human collective behaviors in the speci c scenario of a sudden catastrophe, this catastrophe can be natural (i.e. earthquake, tsunami) or technological (nuclear event). The novelty of our work is to propose a mathematical model taking into account di erent concurrent behaviors in such situation and to include the processes of transition from one behavior to the other during the event. Here, we focus more on the sequence of behaviors since our aim is to better apprehend and handle the collective reactions. In the literature, several models have been proposed for modeling crowd dynamics, both at microscopic (through agent-based simulation frameworks), and at macro-scopic level (via PDE equations). However, generally, the human reactions are classi ed in a single category, very often that of panic and the sequences of di fferent human behaviors are rarely considered, while in Human Sciences these concepts have already been addressed. Thus, in this multidisciplinary research included mathematicians, computer scientists and geographers, we take into account the psychological reactions of the population in situations of disasters, and we study their propagation mode. We propose a SIR-based model, where three types of collective reactions occur in catastrophe situations: re flex, panic and controlled behaviors. Moreover, we suppose that the interactions among these classes of population can be realized through imitation and emotional contagion processes. Finally, numerical simulations have been carried out to validate and compare our model with the experimental data available in the literature.